Rami Messalem

Fate of antibiotics in activated sludge followed by ultrafiltration (CAS-UF) and in a membrane bioreactor (MBR).

The fates of several macrolide, sulphonamide, and trimethoprim antibiotics contained in the raw sewage of the Tel-Aviv wastewater treatment plant (WWTP) were investigated after the sewage was treated using either a full-scale conventional activated sludge (CAS) system coupled with a subsequent ultrafiltration (UF) step or a pilot membrane bioreactor (MBR) system. Antibiotics removal in the MBR system, once it achieved stable operation, was 15-42% higher than that of the CAS system. This advantage was reduced to a maximum of 20% when a UF was added to the CAS. It was hypothesized that the contribution of membrane separation (in both systems) to antibiotics removal was due either to sorption to biomass (rather than improvement in biodegradation) or to enmeshment in the membrane biofilm (since UF membrane pores are significantly larger than the contaminant molecules). Batch experiments with MBR biomass showed a markedly high potential for sorption of the tested antibiotics onto the biomass. Moreover, methanol extraction of MBR biomass released significant amounts of sorbed antibiotics. This finding implies that more attention must be devoted to the management of excess sludge.

Novel ion-exchange spacer for improving electrodialysis II. Coated spacer

Ion-conducting spacers were prepared by applying an ion-exchange coating to commercially available polypropylene netting. Homogeneous and heterogeneous types of coating were used. Homogeneous anion-exchange coating consisted of bromomethylated and aminated polysulfone, homogeneous cation-exchange coating of sulfonated polysulfone. All heterogeneous coatings consisted of ground ion-exchange resin, embedded in crosslinked poly(vinyl alcohol). All the coated spacers increased the rate of desalting of sodium chloride solutions, at concentrations of 20 mM or less. The effect increased with the ion-exchange capacity of the spacer per unit area. The spacers suppress polarization, leading to increased current efficiency and decreased cell resistance. As expected, largest decrease of cell resistance is obtained in dilute solutions, <3 mM. The clearest effect on efficiency was observed in ED with heterogeneous ion-exchange membranes, which are by themselves highly polarizing. Most experiments were carried out with anion-exchange spacers, minimizing the water splitting which takes place at the surface of the ion-exchange membrane. Introduction of an anion-exchange spacer near the heterogeneous anion-exchange membrane and a cation-exchange spacer near the heterogeneous cation-exchange membrane led to a dramatic increase in current efficiency.

Comparison of two treatments for the removal of selected organic micropollutants and bulk organic matter: conventional activated sludge followed by ultrafiltration versus membrane bioreactor

The potential of membrane bioreactor (MBR) systems to remove organic micropollutants was investigated at different scales, operational conditions, and locations. The effluent quality of the MBR system was compared with that of a plant combining conventional activated sludge (CAS) followed by ultrafiltration (UF). The MBR and CAS-UF systems were operated and tested in parallel. An MBR pilot plant in Israel was operated for over a year at a mixed liquor suspended solids (MLSS) range of 2.8-10.6 g/L. The MBR achieved removal rates comparable to those of a CAS-UF plant at the Tel-Aviv wastewater treatment plant (WWTP) for macrolide antibiotics such as roxythromycin, clarithromycin, and erythromycin and slightly higher removal rates than the CAS-UF for sulfonamides. A laboratory scale MBR unit in Berlin - at an MLSS of 6-9 g/L - showed better removal rates for macrolide antibiotics, trimethoprim, and 5-tolyltriazole compared to the CAS process of the Ruhleben sewage treatment plant (STP) in Berlin when both were fed with identical quality raw wastewater. The Berlin CAS exhibited significantly better benzotriazole removal and slightly better sulfamethoxazole and 4-tolyltriazole removal than its MBR counterpart. Pilot MBR tests (MLSS of 12 g/L) in Aachen, Germany, showed that operating flux significantly affected the resulting membrane fouling rate, but the removal rates of dissolved organic matter and of bisphenol A were not affected.

Techno-economic analysis of combined concentrating solar power and desalination plant configurations in Israel and Jordan

Abstract Combined concentrating solar power (CSP) and desalination plants represent a realistic future option for the production of electricity and fresh water for countries of the world’s sunbelt. In this paper, parabolic trough power plants for electricity production have been analysed in combination with multi-effect distillation (MED) and ultrafiltration/reverse osmosis (RO) desalination plants for two sites in Israel (Ashdod) and Jordan (Aqaba). Both RO and MED desalination plants were designed for a fresh water production capacity of 24,000 m3/d. The power block of the CSP plant was selected to meet the steam consumption of the MED plant at the design point, which led to a gross electrical power generation capacity of the power block of 42 MWel. Due to the low availability and generally high cost of coastal land, the CSP + RO plant consists of two separate units. It was assumed that the CSP plant is located at an inland location where there is land available. The RO plant is located at the sea, whil...

Wastewater Reclamation for Agricultural Reuse in Israel: Trends and Experimental Results

Water shortage and a deterioration in the quality of water resources in Israel have made necessary a national policy recommending reuse of practically all municipal wastewater in order to supply a major part of agricultural water demand. Two pilot-scale systems were operated and studied for several years. The first one consisted of an advanced treatment scheme incorporating a sequencing batch reactor (SBR) system with further deep-bed granular filtration. The second system was an SBR unit, for the purpose of optimizing nitrogen and phosphorus removal and testing further microfiltration of SBR effluents. The SBR process has been shown to be an efficient biological treatment method producing low Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) effluents. SBR effluents, even if loaded with high TSS concentrations, could be further purified in the filtration stage, producing low-turbidity effluents. Granular filtration experiments were carried out using a gravitational single-medium filter composed of uniformly-sieved quartz sand. It was found that most of the suspended solids were removed in the top 10 cm of the filter bed. Influent turbidity was found to be the main parameter affecting the process, while filtration rate had only a minor effect. Microfiltration of SBR effluents showed highly efficient removal of turbidity and pathogens. Advanced mathematical models were developed and calibrated for both the biological process and for the granular filtration process.

Biofilm formation on RO membranes: the impact of seawater pretreatment

AbstractMembrane biofouling is an acute problem that interferes with filtration and pressure-driven desalination processes. In this study, ultrafiltration (UF) and membrane bioreactor (MBR) system were examined for their potential use in the removal of organic matter from seawater as pretreatment for reverse osmosis (RO) desalination. The study showed that MBR treatment equipped with UF decreases total organic carbon, polysaccharides, and biofouling potential of RO membrane in comparison to feed seawater after UF treatment alone. Bacteria in the feed water and in the MBR system were characterized. The most abundant heterotrophic bacteria nourished from organic substances present in the MBR system belonging to the Alphaproteobacteria and Gammaproteobacteria classes increased from ~40% in seawater to ~60% in the MBR. These results indicate that pretreatment using a seawater MBR system can improve RO feed water quality and reduce the biofouling potential of RO membranes.

Solar desalination for sustainable brackish water management in arid land agriculture

An agricultural facility aimed at sustainable production of crops in arid environments was built and tested in Hatzeva, Israel. The facility relies on solar-powered desalination with nanofiltration membranes to treat the local brackish water (EC=2.32dSm �1 ) and produce high-quality irrigation water (EC=0.71dSm �1 ). Red beet, a salt-tolerant crop, was grown with the concentrate stream (EC=4.73dSm �1 ), eliminating the need for concentrate disposal and with potential net economic benefits. Agricultural experiments with variable irrigation water quality, application rate, and four staple crops (potato, maize, millet and sorghum) were conducted over two growing seasons between September 2010 and June 2011. The desalination plant operated at low pressure (4.3 bar) and energy consumption (1.37kWhm �3 ) and with little maintenance over the entire study period. The results of the agricultural experiments consistently showed that irrigation with desalinated water promoted more efficient use of resources such as water and inorganic fertilizers. A reduction of 25% in the irrigation rate and use of fertilizers compared with best-practice guidelines was achieved with desalinated water, with no detectable detrimental effect on the marketable yield. On the contrary, a statistically significant yield increasewasobservedforsorghum (+10%).Anincreaseinwaterproductivitywithdesalinatedwaterwasobservedforall four staple crops.

MEMBRANES FOR UNRESTRICTED WATER REUSE

Water reuse is becoming a key component of the water cycle management.The provision of sufficient and safe water supplies for human and environmental needs is a difficult challenge in many parts of the world, especially in arid regions. In order to manage water resources in an efficient and sustainable way, a wide range of tools and techniques are required. Water recycling and reuse is an increasingly important element of sustainable water management strategies in both water poor and water rich regions. Municipal wastewater, which comprises between 60-80% of municipal water consumption, is one of the most reliable sources of water, since municipal water supply is always of high priority. If treated properly, it can replace potable water and used for unrestricted irrigation, including edible crops. Membrane separation processes such as ultrafiltration (UF) and microfiltration (MF) hold the key to better water treatment as tertiary filtration, after existing biological treatment. Careful evaluation of engineering aspects of these filtration technologies will yield design and operation parameters for applications in Europe. A few case studies will be presented. Economic analysis was carried out, for a system that produces a net effluent capacity of 25,000m 3 /day, resulted in a total cost of 8-10 cent per cubic meter. Recently, Membrane Bioreactor Systems (MBR) are becoming an attractive alternative, especially for limited space constrains, taking into advantage their smaller footprint, as compared to conventional wastewater systems. Also, the higher qualities of their effluent, with SDI values lower than 3, indicate the suitability of the process for pre- treatment for desalination by Reverse Osmosis, for effluents with high salinity. The concept of Integrated Membrane Systems (IMS) will be elaborated, and case studies will be described.

WATER DETOXIFICATION AND DISINFECTION USING HIGH SOLAR CONCENTRATION AND HOMOGENEOUS PHOTOCATALYSTS

The objectives of the research were to explore the use of concentrated sunlight combined with dissolved photocatalysts to improve water quality. Initial experiments with bromacil using organic-dye photosensitizers indicated that the reaction kinetics were enhanced by concentrated light. Other pesticides (EPTC, Tribufos, Atrazine and Lindane) were also tested in normal and concentrated sunlight. Organic dyes were effective in degrading some of these compounds but did not appear to be promising for complete mineralization. For most target compounds, the reaction rates were approximately proportional to the intensity of light. Iron compounds, especially in combination with hydrogen peroxide as the oxidizer, proved to be effective for degrading all the target pesticides. This system was also shown to mineralize phenol. Reaction rates were again approximately proportional to sunlight intensity. The photoefficiency of this reaction was in a range high enough to indicate that visible light, as well as UV, was participating in the photo-reactions. Preliminary disinfection tests have indicated that either organic dyes or iron compounds are effective. It is concluded from this work that solar irradiation with either organic dyes or the iron-peroxide system are a promising, possibly low cost, means of improving water quality.

New bipolar membrane setup for high current densities

Limited affordable current density of ca. 0.2 A cm �2 is a major drawback in bipolar membrane (BPM) electrodialysis technology. At higher current densities, the diffusion of water into the BPM interface between the anion and cation exchange layers becomes the rate-limiting step for the water dissociation process. The extended use of the BPM setup at such high current densities, however, results in dehydration of the membrane, an increase in its resistance, and irreversible damage to the BPM. A new experimental setup intended to enable high current densities to be safely used is described. The setup comprises a BPM made of a commercial anion exchange membrane to which a thin (<60 μm) sulfonated polyphenyl sulfone layer (TCL) is glued. Between the TCL and an adjacent commercial cation exchange membrane, a solution of polystyrene sulfonic acid (PSSA) is circulated through a net. This setup enables water to diffuse at a high rate through the TCL into the interface where the dissociation process occurs. The composition of the circulating solution prevents the excessive leakage of anions through the TCL into the solution of the basic product. Current densities of 0.4–0.5 A cm �2 were achieved with comparatively low voltage drops on the